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A broadband superconducting detector suitable for use in large arrays


Cryogenic detectors are extremely sensitive and have a wide variety of applications1,2,3 (particularly in astronomy4,5,6,7,8), but are difficult to integrate into large arrays like a modern CCD (charge-coupled device) camera. As current detectors of the cosmic microwave background (CMB) already have sensitivities comparable to the noise arising from the random arrival of CMB photons, the further gains in sensitivity needed to probe the very early Universe will have to arise from large arrays. A similar situation is encountered at other wavelengths. Single-pixel X-ray detectors now have a resolving power of ΔE < 5 eV for single 6-keV photons, and future X-ray astronomy missions7 anticipate the need for 1,000-pixel arrays. Here we report the demonstration of a superconducting detector that is easily fabricated and can readily be incorporated into such an array. Its sensitivity is already within an order of magnitude of that needed for CMB observations, and its energy resolution is similarly close to the targets required for future X-ray astronomy missions.

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Figure 1: An illustration of the detection principle.
Figure 2: A microscope photograph of the device tested.
Figure 3: The microwave measurement set-up and the phase calibration of the detector. A low-phase noise microwave synthesizer (right inset) generates the fixed-frequency signal used to excite the detector, which is cooled in a dilution refrigerator.
Figure 4: Single-photon X-ray pulses measured at 70 and 300 mK.
Figure 5: A plot of the noise measured for the test device; several other devices have given similar results.


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This work has been supported in part by NASA (Aerospace Technology Enterprise), the JPL Director's Research and Development Fund, and the Caltech President's Fund. We are grateful for the support of A. Lidow, Caltech Trustee.

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Correspondence to Peter K. Day.

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Day, P., LeDuc, H., Mazin, B. et al. A broadband superconducting detector suitable for use in large arrays. Nature 425, 817–821 (2003).

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